1. Field of the Invention
The invention relates to a recording method of an optical disc drive, and more particularly, to a method for choosing recordable speeds by verifying results of testing write powers while the optical disc drive records data onto an optical disc.
2. Description of the Prior Art
An optical disc drive emits a laser beam irradiated from an optical pick-up head on a recordable optical disc to form marks, such as pits or phase changes, where different reflected laser intensities of a marked area and an unmarked area can be utilized to distinguish digital values 1 and 0. In this way, the goal of recording data on the optical disc is achieved. Therefore, the quality of marks recorded on the optical disc depends on the laser power and the irradiation time. However, the irradiation time is decreased when the rotation speed of the optical disc increases.
Although the quality of marks recorded on the optical disc is better when the rotation speed is slower and the irradiation time is longer, the recording performance of the optical disc drive is degraded due to the fact that slower rotation speed of the optical disc makes the recording time inevitably increase.
The capacity of optical discs has become larger and larger. In order to shorten the recording time, as shown in FIG. 1, a conventional optical disc drive rotates an optical disc 2 by a spindle motor 1, moves an optical pick-up head 3 in a radial direction back and forth, and uses the optical pick-up head 3 to irradiate a laser beam onto the optical disc 2. Because the outer tracks of the optical disc 2 have higher tangential velocity, the optical disc 2 is divided into several areas from the inner track to the outer track according to different recording speeds. By changing addresses under default recording speeds which vary from a low recording speed to a high recording speed step by step, such as 2×, 4×, 6× and 8×, the recording speed of the outer track is increased to thereby reduce the overall recording time.
However, as there are many manufacturers that produce optical discs 2, the materials, ingredients and manufacturing processes of the optical discs 2 made by different manufacturers might be different. This makes optical discs 2 manufactured by different manufacturers have different reflective characteristics in response to the laser beam. Therefore, the conventional optical disc 2 is configured to have the most inner track and the most outer track respectively serving as an inner track test area 4 and an outer track test area 5 for testing the laser power to obtain an optimum laser power used for recording data onto the optical disc. A conventional optical disc drive performs a recording test by recording default test data at the inner track test area 4 or the outer track test area 5 at a low recording speed 2×, and then reads out data which has been recorded onto the optical disc 2 by the recording test. Next, a recording quality parameter (e.g., a Beta parameter) used for evaluating the recording quality of the marks is derived by the amount of reflected light corresponding to recorded marks, decoding error rate, signal intensity, etc. An Optimum Power Control (OPC) is implemented to choose the optimum write power in accordance with a plurality of recording quality parameters derived from the recording test. To shorten the recording time required by the recording test, the write powers of higher recording speeds are estimated using the optimum write power of the low recording speed 2× and ratios between the low recording speed 2× and the higher recording speeds. After the optimum laser powers for different recording speeds are successfully derived, the conventional optical disc drive proceeds with normal data recording.
However, the conventional optical disc drive does not obtain the write power used for high recording speed from an actual test; instead, the conventional optical disc drive directly derives the recording power used for high recording speed from a test result of recording default data at the low recording speed, which makes it difficult to control the recording quality of the higher recording speeds of the optical disc. What is worse is that the optical disc even has bad readability of recorded data or is unreadable. However, implementing a recording test for each recording speed takes up more test areas, which reduces capacity available for normal data storage of the optical disc, and also makes it necessary to prepare, transfer and record the default test data of the recording test applied to each recording speed. This lengthens the recording time and degrades overall recording performance. Besides, the optical disc drive cannot support optical discs made by all manufacturers. While implementing a recording test on an unsupported optical disc, the optimum write power derived from recording limited default data at a lowest recording speed may not have acceptable recording quality, not to mention the estimated write powers for higher recording speeds. Therefore, the conventional recording test employed in the optical disc drive still has problems to be worked out.